模拟酸雨对亚热带三个树种凋落叶分解速率及分解酶活性的影响

利用凋落物袋法研究了模拟酸雨对中国亚热带地区3个典型树种杉木(Cunninghamia lanceolata)、香樟(Cinnamomum camphora)、银杏(Ginkgo biloba)凋落叶分解速率及酶活性的影响.酸雨分别设置为重度酸雨(pH=2.5)、中度酸雨(pH=4.0)、对照处理(pH =5.6)3个梯度.试验结果表明:酸雨胁迫会抑制凋落叶的分解,且随着酸雨强度的增强,抑制作用更明显.杉木、香樟、银杏3个树种对照处理下周转期分别比中度酸雨短33％、43％、14％,比重度酸雨短44％、52％、17％.3种分解酶对酸雨胁迫的表现不同,脲酶和纤维素酶表现为一定的抑制作用,基本呈现为对照处理(pH=5.6)＞中度酸雨(pH=4.0)＞重度酸雨(pH=2.5),与凋落物的分解速率排列情况一致,蔗糖酶在酸雨胁迫下反而有激活的趋势,表现为重度酸雨(pH=2.5)＞中度酸雨(pH =4.0)＞对照处理(pH=5.6).不同树种对酸雨胁迫的影响有一定的差异性,针叶树种杉木受影响最大,阔叶树种香樟和银杏受影响较小,银杏的抗酸性较强,且针叶树种的分解速率比阔叶树种慢.脲酶和纤维素酶对凋落叶的分解贡献较大,而蔗糖酶的影响相对较小.酶活性与季节有较大的关系,夏季活性相对偏高,冬季活性相对偏低.     

盐度对湿地枯落物分解过程中碳氮磷化学计量比的影响

为了阐明盐度对枯落物分解过程中碳氮磷化学计量比的影响,采用分解袋法对闽江河口湿地不同盐度条件下短叶茳芏枯落物和芦苇枯落物分解过程中生态化学计量学特征进行了测定.结果表明,盐度较高的生境,枯落物具有较快的分解速率、氮和磷的释放速率,较慢的碳和能量释放速率;整个分解期间内,枯落物C/N呈下降的趋势,C/P和N/P表现为先上升后下降的趋势;高盐度生境短叶茳芏枯落物和芦苇枯落物分解过程中平均C/N、C/P和N/P分别为34.3和36.4、1210.4和1710.3、35.4和47.1;低盐度生境短叶茳芏枯落物和芦苇枯落物分解过程中平均C/N、C/P和N/P分别为33.2和35.1、1170.0和1636.8、35.9和47.3;高盐度生境短叶茳芏枯落物和芦苇枯落物C/N、C/P高于低盐度生境,N/P低于低盐度生境;较低的枯落物碳与养分比值具有较高的能量释放.     

Fate of arsenic compounds in poultry litter upon land application

The use of the organic As compound, roxarsone, as an antibiotic additive to poultry feed continues to raise concern over potential negative environmental impacts. Total As concentration in poultry litter can reach >40 mg kg⁻¹ and both roxarsone and its mineralization product As(V) have been identified in poultry litters (PL). To investigate the fate of these As species upon land application of PL we conducted two studies. In the first, an Orangeburg soil (Ultisol from the Atlantic Coastal Plain) was spiked with either 20 mg kg⁻¹ As(V) or roxarsone and incubated at 10% moisture content for 4 months. Exchangeable As was determined periodically by extraction with 0.1 M PO₄. Both As(V) and roxarsone displayed similar desorption; initially, approximately 70% of added As was ligand exchangeable and this decreased to 35% after 4 months incubation, presumably due to either slow sorption reactions or a change in solid phase speciation of As to less exchangeable forms. In the second study, various manipulations of two PL samples were applied to the Orangeburg soil at realistic field application rates. The treatments were wet to 10% moisture content and water soluble As, Cu and organic carbon (DOC) was measured over 30 days. Arsenic and Cu solubility were highest from the dried litter samples. Ashing of the PLs decreased soluble As and Cu, presumably because of the loss of organic matter from the ashed litter and subsequent decrease in DOC. Application of leachates from either PL resulted in higher concentrations of soluble As and Cu than when the soil was amended with equivalent concentrations of soluble As and Cu dissolved in DI H₂O. We hypothesize that the increased levels of DOC from the PL treatments enhance As and Cu solubility through competitive sorption and complexation, respectively. In fact, As and Cu solubility was correlated to DOC levels in the amended soil extracts. Even though land application of PL introduced relatively low concentrations of As and Cu to soil it appeared that other soluble constituents of PL significantly enhanced As and Cu solubility.     

Identification of various laccases induced by anthracene and contribution to its degradation in a Mediterranean coastal pine litter

Mediterranean coastal ecosystems are known to be highly subject to natural and anthropic environmental stress. In this study, we examine the effects of anthracene as a common pollutant on the total microbial communities from a Pinus halepensis litter of a typical Mediterranean coastal site (Les Calanques, Marseille). The main objective was to identify the microbial factors leading the resilience of this ecosystem. Two questions were addressed: (i) how lignin-degrading enzymes (Laccase, Lignin-peroxidase and Mn-peroxidase) are affected by the presence of this molecule, (ii) whether the indigenous consortia are involved in its degradation in mesocosms under favorable incubation conditions (25 °C, 60% WHC) and after different time intervals (1 and 3 month(s)). We found a strong increase in laccase production in the presence of anthracene after 3 months, together with anthracene degradation (28% ± 5). Moreover 9,10-anthraquinone is detected as the product of anthracene oxidation after 3 months. However neither lignin-peroxidase activity nor Mn-peroxidase activity is detected. Laccase proteins directly extracted from litter were sequenced via Nano-LC-MS/MS and reveal twelve different peptide sequences induced by the presence of anthracene in the mesocoms. Our study confirms the major detoxification role of this enzymatic system and highlights the high degradation potential of fungal species inhabiting P. halepensis litter, a factor in the resilience of Mediterranean ecosystems.     

长期地上凋落物处理和氮添加对油松-辽东栎混交林表层土壤碳氮组分的影响

气候变化引起的土壤碳源和氮源输入变化对森林生态系统碳、氮动态有潜在的重要影响.了解不同团聚体和化学成分的碳、氮组分对碳源和氮源输入的响应,对进一步揭示和预测未来气候变化下土壤碳、氮的响应特征具有重要意义.为了探究土壤不同碳、氮组分及其计量比对土壤碳源和氮源输入变化的响应特征,本研究基于在温带油松-辽东栎混交林样地建立的长期（8年）地上凋落物处理和氮添加实验,测定和分析了土壤不同团聚体碳、氮组分、可溶性碳、氮组分和微生物生物量碳、氮等指标.结果表明：长期叶凋落物加倍和混合凋落物加倍（含枝、叶和球果）均显著增加了土壤总有机碳、全氮、可溶性碳、活性碳及大团聚体（250~2000 μm）和微团聚体（53~250 μm）碳、氮组分的含量;氮添加显著增加了土壤总有机碳、全氮、可溶性氮及活性碳组分的相对和绝对含量;但土壤黏粉粒（2~53 μm和<2 μm）碳、氮组分、微生物生物量碳、氮及各碳、氮组分比值在不同处理之间均无显著性差异;地上叶凋落物加倍和混合凋落物加倍处理显著增强了土壤团聚体的稳定性并降低了土壤可溶性有机质的芳香性.这些结果表明,高质量和数量凋落物的输入及氮添加量的增加显著促进了土壤不同碳、氮组分的含量,但并没有显著改变各碳、氮组分的比值.     

高水分蔬菜废物和花卉、鸡舍废物联合堆肥的中试研究

以滇池流域的典型农业废物蔬菜、花卉废物和鸡舍废物为原料,进行了不同配比的联合堆肥中试研究.一次发酵采用温度反馈通气量控制的静态好氧堆肥系统,二次发酵采用周期性翻堆自然腐熟.在一次发酵阶段,堆体温度在55℃以上保持至少3d,最高温度达73.3℃,可有效杀灭致病菌;堆体含水率从75%降低到56%,多余水分得到快速去除;有机质从65%降低到50%,pH值稳定在8.二次发酵后堆肥产物的腐熟度和养分分析结果表明,产物稳定性好,养分含量高.通过堆肥工艺的优化控制,蔬菜废物、花卉废物和鸡舍废物联合堆肥可以获得高质量的堆肥产品,废物还田能有效减少固体废物非点源污染、提高土壤肥力.     

Nutrient contribution of leaf litter in urban stormwater

This paper investigates the nutrient contribution from leaf litter in urban waterways, using data from a gross pollutant monitoring programme in a 50 ha catchment in an inner-city suburb of Melbourne, Australia. The data indicate that the potential nutrient contribution of stormwater leaf litter (greater than 5 mm) is about two orders of magnitude smaller than the typical nutrient loads in urban stormwater. The results suggest that removing leaf litter from urban waterways will do little to reduce the total stormwater nutrient load.1998 Academic Press     

Phosphorus availability in two soils amended with poultry litter

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杉木林凋落物产量、分解率与储量的关系

在福建三明采用2种方法测定27a生杉木林的杉木叶和小枝凋落物的分解率．采用网袋法(孔径0．5mm尼龙网袋)测定的杉木叶和小枝凋落物残留率Olson指数模型的分解系数(k值)分别为0．7692a^-1和0．2501a^-1，相应的第1年的分解率分别为53．66％和22．13％；另一种测定矗值的方法较为准确，是通过计算凋落物年产量与地面凋落物储量的比值得到，采用该方法计算的杉木叶和小枝凋落物的矗值分别为1．788a^-1和0．8622a^-1，分别是网袋法测定值的2．32和3．54倍，相应的第1年的分解率分别为83．27％和57．78％，分别是网袋法测定值的1．55倍和2．61倍．采用后一种方法测定的凋落物分解率可以解决尼龙网袋法测定分解速率结果偏低的问题．     

Qualitative and quantitative assessment of the risk from the exposure to fetotoxic chemical compounds

A new mathematical dose-response model for the expected probability of toxic response and also for the expected measure of the overdispersion parameter for the reproductive and developmental risk assessment is proposed. The model for the expected probability of toxic response is an improvised Weibull dose-response model incorporating the litter-size effect while the model for the overdispersion parameter is a polynomial function of the dose level. A beta-binomial distribution for the number of offspring showing toxic responses in a litter satisfactorily accounts for the extra-binomial variation and the intralitter correlation of responses of these pups. Confidence limits for low-dose extrapolation are based on the asymptotic distribution of the likelihood ratio. The safe dose for human exposure is then calculated by simple linear extrapolation. The model for overdispersion allows us to obtain the estimates of the overdispersion parameter at these dosages. This was not possible in the earlier models. The proposed model is illustrated by an application to a study on the effect of exposure to diethylhexylphthalate in mice. The results are compared with those obtained by Chen and Kodell (1989) who have applied the simple Weibull dose-response model to the same data set.This paper was prepared with partial support from the United States Environmental Protection Agency under a Cooperative Agreement Number CR-815273. The contents have not been subject to Agency review and therefore do not necessarily reflect the views or policies of the Agency and no official endorsement should be inferred.